DIGESTIVE AND FEEDING BEHAVIOR DIFFERENCES BETWEEN LAPPET-FACED VULTURES (TORGOS TRACHELIOTOS) AND GRIFFON VULTURES (GYPS FULVUS) EX SITU.

Appropriate diets for ex situ wildlife are essential for animal health and welfare and yet ex situ facilities are often constrained by feed ingredient availability when attempting to replicate natural diets. In obligate carnivores such as vultures, digestive strategies are likely to have evolved alongside feeding behaviors, which may differ between even sympatric species. To begin to understand the digestive strategies of two Old World vulture species (lappet-faced vulture Torgos tracheliotos, n = 3, and griffon vulture Gyps fulvus, n = 4) of similar body size but divergent feeding habits, their feeding and digestion strategies on a diet of whole rats were compared. The food intake, color of excreta, excreta consistency, and carbon and nitrogen excretion were measured. Mean retention time of the digesta was analyzed using titanium dioxide as an inert marker in a diet of chicken carcass. Lappet-faced vultures consumed significantly greater quantities of food than griffon vultures and were less selective. Lappet-faced vultures primarily produced brown excreta while griffon vultures primarily produced green excreta, with much higher carbon and nitrogen concentrations. The consistency of excreta and the mean retention time did not differ between the species but may have been too variable to detect differences. A strong positive correlation was found between food intake per metabolic weight and the proportion of brown excreta, and both were negatively correlated with green excreta, as well as excreta concentrations of nitrogen and carbon. These findings align with their reported feeding ecology, with lappet-faced vultures showing adaptations to less-digestible carcass material compared with griffon vultures. Despite their similar size and overlapping natural habitat, these results suggest a need for differentiated feed provisioning for these species when under human care.

Integrating Gut Bacterial Diversity and Captive Husbandry to Optimize Vulture Conservation.

Endangered species recovery plans often include captive breeding and reintroduction, but success remains rare. Critical for effective recovery is an assessment of captivity-induced changes in adaptive traits of reintroduction candidates. The gut microbiota is one such trait and is particularly important for scavengers exposed to carcass microbiomes. We investigated husbandry-associated differences in the gut microbiota of two Old World vulture species using 16S RNA gene amplicon sequencing. Increased abundance of Actinobacteria occurred when vultures were fed quail but not rat or chicken. Conversely, diet preparation (sanitization) had no effect, although bacterial diversity differed significantly between vulture species, likely reflective of evolved feeding ecologies. Whilst the relative lack of influence of a sanitized diet is encouraging, changes in bacterial abundance associated with the type of prey occurred, representing a dietary influence on host-microbiome condition warranting consideration in ex situ species recovery plans. Incorporation of microbiome research in endangered species management, therefore, provides an opportunity to refine conservation practice.